This invention relates to a squaring circuit which is capable of exhibiting a squaring characteristic relative to an input signal or voltage.
Conventionally, a squaring circuit of the type described has been proposed by the instant inventor in a paper which has been contributed to IEICE Transactions on Electronics and which has been published in Vol. E76-C, No. 5, May 1993, page 722. The squaring circuit has a pair of input terminals given an input voltage and a pair of output terminals across which a differential output current appears as an output current. In the squaring circuit, a relationship between the input voltage and the output current is represented by a transfer characteristic which can be approximated by a squaring curve.
More specifically, the squaring circuit proposed in the paper is structured by four transistors driven by a single constant current source. In this connection, the four transistors have emitters connected in common to the constant current source while two of the transistors have bases connected in common to each other so as to be connected to each of the input terminals. In addition, each pair of the transistors has collectors connected in common to each other to provide each of the output terminals.
The squaring circuit mentioned above is called a quadritail cell in the paper because the four transistors are driven by a single tail current source.
At any rate, the four transistors are driven by the single tail current source in the above-mentioned quadritail cell. This means that it is difficult to reduce a current consumed in each transistor. In addition, the squaring circuit mentioned in the paper is disadvantageous in that improvement of a high frequency characteristic inevitably brings about an increase of a drive current.